This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. This protocol is designed to examine why, when food is eaten to satiety, its reward value decreases to zero. This change in the reward value and the rated pleasantness of the sensory input produced by food is one possible way in which food intake is controlled. Based on our fMRI data and published results, we hypothesize that the orbito-frontal cortex is involved in the reward-driven control of food intake. The experiments aim at demonstrating in obese patients a lack of the orbito-frontal cortex inhibition of olfactory inputs that is induced by satiety in normal subjects.